1. Field of the Invention
The present invention relates to a variable displacement compressor, and more particularly to a reduction in vibration and noise due to suction pulsation during variable displacement operation.
2. Description of the Related Art
Conventionally, a piston type compressor is equipped with a stopper so that the suction reed valve may not undergo self-excited vibration at the time of suction. However, in a piston type variable displacement compressor, the suction gas amount differs between the maximum displacement state and the variable displacement state. Thus, when the stopper provided is adjusted to the maximum displacement state, the suction reed valve does not open to a sufficient degree and does not abut the stopper when, in particular, the displacement is small, or when the compressor is started in the OFF state, in which the displacement is minimum. As a result, the suction reed valve generates self-excited vibration to cause suction pulsation, the vibration of which may be propagated to the exterior of the compressor to thereby generate noise.
In this regard, U.S. Pat. No. 6,257,848, for example, discloses a compressor in which there is arranged an opening control valve which controls the opening area of the suction passage, thereby mitigating the fluctuation in pressure when the flow rate is low.
However, in the above construction disclosed in U.S. Pat. No. 6,257,848, the opening control valve is operated by utilizing a pressure difference due to the gas flow in the suction passage and a spring force, so that when priority is given to the throttle effect, a throttle effect is also obtained when the displacement is maximum to thereby cause a deterioration in performance, whereas an attempt to secure the performance corresponding to the maximum displacement makes it impossible to effect throttling to a sufficient degree during small displacement operation, which requires a throttle effect.